The season finale of Grey's Anatomyleft many things on the verge of disaster. Among the most-damaging: Alex revealed that Meredith tampered with the clinical trial, jeopardizing her job and her marriage with finally official husband Derek, and a pregnant Cristina announced she didn't want to have Owen's child.

Before the final year of residency for the Seattle Grace doctors kicks off, executive producer Shonda Rhimes talked to TVGuide.com about the difficulties the docs will face and the future of ABC's long-running medical show:

If last season was about growing up, what is this season about? Shonda Rhimes: This is our last year as residents for Meredith, Cristina, Alex, Jackson and April. It feels like it's a new beginning for everybody in a lot of ways.

How is writing this season different knowing that it is likely the last for a lot of the main castmembers? [The contracts of Ellen Pompeo, Patrick Dempsey and Chandra Wilson, among others, are up after this season.] Rhimes: I don't know about the word "likely" possibly the last. I usually start planning my seasons [by planning the last scene first]. This year, we just don't know. I just don't know what we'll be doing at the end of the year, so we couldn't start out that way. We're doing it a little bit differently this year. I pitched eight different scenarios for the end of this season, but we don't know which ones we're writing to. So right now, we're concentrating on the first half, then we're going to concentrate on the second half as a separate shock.

Among those eight scenarios, is there a possibility this could be the end of Grey's? Rhimes: I don't speak for the network and I don't decide when the show ends, but I can't imagine that that's going to be true.

Has there been any thought to having Lexie (Chyler Leigh) become the Grey of Grey's Anatomy? Rhimes: I feel like Meredith Grey is the Grey of Grey's Anatomy and that's how it goes.

Let's start with Alex (Justin Chambers) and Meredith. He really screwed himself over in outing her for tampering with the Alzheimer's clinical trial. What will we see for him this season? Rhimes: We're going to watch Alex both grow up and backslide a little bit. I think he starts off in a real bad place, like really behind and nobody likes him. He's not doing so well. We're going to watch him pull it together and work to get his friendships back and charge forward.

How will what he did continue to affect Meredith's job as well as her relationship with Derek? Rhimes: I think it affects her job tremendously. What Meredith did has real ramifications for her job and for her relationship, both in her personal and her work relationship with Derek.

You've always said Meredith and Derek are made for each other. How will they find their way back to that this season? Rhimes: They'll struggle. They're grown-ups, and what's nice about this is that it's about more than that now. They have a child and they're in a much more mature place than they have been in the past. They made vows and they have a Post-It, which is really the most important piece of paperwork that they have. It's not really about Meredith and Derek breaking up forever, I think people's marriages get screwed up. People have to work to fix them.

Will there be a possibility of seeing the "dark and twisty" Meredith this season? Rhimes: I think Meredith is always dark and twisty, no matter what. I don't think I've ever written a happy, shiny Meredith.

Cristina's new pregnancy harkens back to when she got pregnant in Season 1 by Dr. Burke. What will she go through this time around? Rhimes: I think it does harken back to that. What we liked about that, and what I felt really strongly about that, is that Cristina (Sandra Oh) has always had a certain stance in how she feels about having kids and that stance doesn't change just because she's married and in love with Owen (Kevin McKidd). I think that there's something interesting when someone absolutely doesn't want children. I find it an interesting character. People get vilified for that in our society and I think it's really unfair because I feel like if someone doesn't want a kid, they shouldn't have to have one.

Speaking of pregnancies, news broke yesterday that Sarah Drew is expecting. Is it too soon to say whether that's being written into the story, especially because her character is a virgin? Or will she do pre-shoots like Ellen and Jessica Capshaw did? Rhimes: April Kepner is a virgin and we'd have to work really fast to get April unvirginized, pregnant and having a baby by January. That feels a little insane, so I don't think we want to speed that story up. We're quite good at hiding things like that, so we'll do what we always do.

How will April handle being Chief Resident? Rhimes: Oh, like April would. It's a lot of anxiety and many, many mishaps. I think it's going to be fun. We're having a really good time with it. I love the idea that there's this person that everybody kind of hates, yet they all have to deal with, [and even] lean on. She is one of them, even though they find her terribly annoying, and I think that that's sort of charming. And while her title is being in charge of them it's a near-impossible task.